Instead of using '.' like your directory, reference its absolute path:
for file in DirectoryWalker(os.path.abspath('.')):
print file
Also, I would recommend using a word other than "file" because it means something in python. Not a keyword, although it still executes.
Aside, when dealing with file names, I find the os.path module incredibly useful - I would recommend looking at it, especially
os.path.normpath
( ) "theFolderYouWereJustIn/../" )
os.path.join